The resolving power of a time-of-flight mass spectrometer in general is decisively determined by the initial pulse length of the ion bunch generated in the ion source. Therefore the ions are usually generated in the ion source by an electrical pulse or laser or particle pulse having lengths which are as short in time as technically possible. When ions are generated by means of these methods, either elaborate pulsed laser systems are needed which are partly combined with pulsed lasers, for positioning of the desorbed neutral particles, or a high electronic and instrumentation effort is required to generate a very short and intense particle pulse that causes the ionization.
The invention is a decisive advance because the pulsed ion generation can be dispensed with and can be replaced by a much more easily implemented continuous ion generation with the same ionization mechanisms.
To extract ions from a relatively large volume, the construction of and the potential distribution in the new ion source allows to use of electrical pulses that are relatively long and thus technically easily can be achieved.